1. Field of the Invention
The present invention relates to a human CC chemokine protein (i.e., a cytokine having the first two of its four cysteine residues adjacent as indicated by “CC”) and to polynucleotides encoding this protein.
2. Background Information
The discovery of IL-8, in 1987, revealed the existence of a novel class of small cytokines, now called chemokines, that are widely studied because of their ability to activate leukocytes and their potential role as mediators of inflammations. A number of different human chemokines have been identified after IL-8, by cloning or biochemical purification and amino acid sequencing. All have four conserved cysteines that form characteristic disulfide bonds, a short amino-terminal and a longer carboxy-terminal sequence. Two subfamilies are distinguished by the arrangement of the first two cysteines, which are either separated by one amino acid (CXC chemokines) or are adjacent (CC chemokines.). Chemokine cDNAs typically encode proteins of 92–99 amino acids in length that are secreted after cleavage of a leader sequence of 20–25 amino acids. Modeling on the basis of the NMR-derived structure of IL-8 suggests that CXC and CC chemokines are folded in a similar manner.
The first human CC chemokine was identified by differential hybridization cloning and was termed LD78 (Obaru, K. Fukuda, M., Maeda, S. and Shimada, K. (1986) J. Biochem. (Tokyo) 99, 885–894.) Several cDNA isoforms of a closely related human chemokine, Act-2, were later described (Miller, M. D. and Krangel, M. S. (1992) Crit. Rev. Immunol. 12, 17–46), and two similar proteins, macrophage inflammatory protein 1α (MIP-1α) and MIP-1β, were purified form the culture medium of lipopolysaccharide (LPS)-stimulated mouse macrophages (Wolpe, S. D., Davatelis, G. Sherry, B. et al. (1988) J. Exp. Med. 167, 570–581). On the basis of more than 70% amino acid identity, the murine and human proteins are considered as homologs, and the terms human MIP-1α and MIP-1β are commonly used instead of LD78 and Act-2. The best characterized CC chemokine is monocyte chemotactic protein 1 (MCP-1), which was purified and cloned from different sources (Miller, M. D. and Krangel, M. S. (1992) Crit. Rev. Immunol. 12, 17–46; Yoshimure, T. Robinson, E. A. Tanaka, S. Appella, E. and Leonardo, E. J. (1989) J. Immunol. 142, 1956–1962; Matsushima, K., Larsen, C. G., DuBois, G. C. and Oppenheim, J. J. (1989) J. Exp. Med. 169, 1485–1490). Other CC chemokines, I-309 (Miller, M. D., Hata, S., De Waal Malafyt, R. and Krangel, M. S. (1989) J. Immunol. 143, 2907–2916), RANTES (Schall, T. J. Jongstra, J., Dyer, B. J. et al. (1988) J. Immunol. 141, 1018–1025) and HC14 (Chang, H. C., Hsu, F., Freeman, G. J., Griffin, J. D. and Reinherz, E. L. (1989) Int. Immunol. 1, 388–397), were purified or cloned as products of activated T cells. HC14, termed MCP-2, was also isolated from osteosarcoma cell cultures (Van Damme, J. Proost, P., Lenaerts, J-P. and Opdenakker, G. (1992) J. Exp. Med. 176, 59–65), along with a novel CC chemokine, MCP-3, which was subsequently cloned and expressed (Minty, A. Chalon, P. Guillemot, J. C. et al. (1993) Eur. Cytokine Netw. 4, 99–110; Opdenakker, G. Froyen, G. Fiten, P., Proost, P. and Van Damme, J.(1993) Biochem. Biophys. Res. Commun. 1991, 535–542). These CC chemokines share a sequence identify with MCP-1 of between 29 and 71% (MCP-2 and MCP-3 have 62–71% identity with MCP-1).
MCP-1, the prototype of the CC chemokine sub-family, is chemotatic for monocytes but not for neutrophils (Yoshimure, T. Robinson, E. A. Tanaka, S. AppelIa, E. and Leonardo, E. J. (1989) J. Immunol. 142,1956–1962; Matsushima, K, Larsen, C. G., DuBois, G. C. and Oppenheim, J. J. (1989) J. Exp. Med. 169, 1485–1490) and was initially considered to be a counterpart of IL-8. Indeed, monocytes respond to all CC chemokines, as judged from stimulus-dependent [Ca2+]i changes (Miller, M. D. and Krangel, M. S. (1992) Crit. Rev. Immunol. 12, 17–46; Bioschoff, S. C., Krieger, M. Brunner, T. et al. (1993) Eur. J. Immunol. 23, 761–767; McColl, S. R., Hachicha, M., Levasseur, S., Noete, K. and Schall, T. J. (1993) J. Immunol. 150, 4550–4560). MCP-1, MCP-2 and MCP-3 induce monocyte infiltration on intradermal injection into rats and rabbits (Van Damme, J. Proost, P., Lenaerts, J-P. and Opdenakker, G. (1992) J. Exp. Med. 176, 59–65; Zacha, C, O. C., Anderson, A. O., Thompson, H. L. et al. (1990) J. Exp. Med. 171, 2177–2182), and MCP-1 also elicits in monocytes a respiratory burst (Miller, M. D. and Krangel, M. S. (1992) Crit. Rev. Immunol. 12, 17–46) and the expression of β2 integrins (Jiang, Y., Beller, D. I., Frendi, G. and Graves, D. T. (1992) J. Immunol. 148, 2423–2428).
While the view that CXC chemokines act on neutrophils and CC chemokines act on monocytes apparently remains valid, recent studies have revealed that CC chemokines have a much wider range of biological activities since they can also activate some lymphocytes and, in particular, basophil and eosinophil leukocytes. Thus, there is a continuing need in the art for isolating novel CC chemokines.